Waveguides are physical structures that guide the propagation of waves, such as sound waves or electromagnetic (radio) waves. In operation, waveguides physically restrict the expansion of a wave to minimize signal energy loss over distance. For example, an acoustic wave emitted from a spherical point source loses energy according to the inverse square law over distance as it radiates into three dimensional space. If an acoustic source is coupled to a waveguide, however, the sound energy is contained until it can be redirected as desired.
Loudspeakers employed in sound systems for boats are typically mounted in side bulkheads, similar to sound systems for vehicles such as automobiles and trucks where the loudspeakers are mounted in the vehicle doors. Door-mounted loudspeakers work reasonably well in vehicles because of the enclosed cabin to contain the acoustic energy and prevent wind noise, which allows adequate sound volume and quality. Mounting loudspeakers in the bulkheads of boats is less effective because the cockpits or helms of boats are typically open to the air with essentially no enclosure. This allows the acoustic energy from loudspeakers to dissipate quickly as it radiates into space. Further, using such mounting arrangement in boats, if the speaker is not facing the occupants some frequencies may seem entirely absent because midrange and high-frequency sound is very directional. Additionally, boat helms are designed for easy access, with the assumption that occupants will frequently move around on deck and be less static than an automotive passenger.
Typical ski boats, bow riders, wakeboard boats and deck boats do not have a cabin or enclosed helm but are usually equipped with a windshield running entirely across the width of the deck for the protection of passengers. Often the entertainment areas of such boats are on the aft deck located behind, but relatively far away from, the windshield. With the noise of the open deck, providing loud, quality sound in the entertainment areas, and especially behind the boat, is often a challenge.